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Category Archives: Evolution

One of the things I enjoy saying the most about my experience with wildlife rehabilitation is that I have worked with raptors – birds of prey like owls, hawks, and falcons. They are amazing, interesting birds but I’ll admit that part of that fun is that when people hear “raptor” they often imagine this:

This association is probably partly due to the blockbuster “Jurassic Park” and other dinosaur movies. A major theme of the film, and one that I love as a student of evolutionary anthropology, is demonstration of the bird-dinosaur relationship. The species Compsognathus is described as walking chicken-like, and the final scene of Jurassic Park shows a flock of birds flying from Isla Nublar and the dinosaurs that dwell on it. After Dr. Alan Grant is laughed at for stating that dinosaurs obviously became birds, he retorts with this:

“Well, maybe dinosaurs have more in common with present-day birds than they do with reptiles. Look at the pubic bone: turned backward, just like a bird. Look at the vertebrae: full of airsacs and hollows, just like a bird. And even the word ‘raptor’ means ‘bird of prey.’”

However, this quote implies that there was foresight in the naming of both birds of prey and certain dinosaurs “raptors” because birds are the evolutionary descendants of some dinosaur species. But the way in which language evolves through translation and interpretation means one cannot assume that the naming intentional. And in terms of the history of the knowledge of evolution, this naming was actually more of a coincidence.

The word “raptor” comes from a Latin verb rapere “to seize by force”. Birds of prey are called raptors because of they way they hunt, seizing their prey out of the air, and Websters dictionary first defined birds of prey as raptors in 1823.

The term “velociraptor”, and other species containing the suffix -raptor, probably originated in scientific literature around 1924. They were so named because velox means “swift” and so velociraptors were thought to be speedy predators who seized their prey.

However, both of these groups received their designation as “raptor” long before paleontologists were able to link birds as the descendants of dinosaurs. The evidence of the bird-dinosaur evolutionary lineage was not concretely supported until the 1980s when dinosaur phylogeny was more fully understood with increasing knowledge of genetics, phylogeny, and evolution.

Assuming that the two share a name because they share an ancestor is a false cause logical fallacy, meaning that a false assumption is made when one believes a relationship seen between two things automatically implies one caused the other. In fact birds of prey and some dinosaur species were named before their evolutionary relationship was understood and so their name was more a convenient coincidence of word choice.

If early orinthologists had decided that birds of prey didn’t seize their prey but rather grabbed, snatched, clasped, clutched, or caught them, the Latin translation never would have matched the dinosaur term that came later.

Fad diets, as their name suggests, are easy-to-follow and trendy diets focused more on short-term success than long-term maintenance of health and weight. Focus is usually placed on eliminating or emphasizing a particular food group for health benefits.

However these diets tend to be difficult and sometimes even dangerous to follow for long periods of time. The Paleo Diet is considered by many to be a fad diet, which I why I was surprised that it is still a somewhat prevalent.

The Paleo Diet, short for Paleolithic Diet, is based on the diet of the early humans (called hominids) which lived during the Paleolithic era of 2.5 million years ago to 10 thousand years ago. It is believed to follow the general “ancestral human diet”.

It claims that humans are most adapted to the diet of their Paleolithic ancestors – fish, eggs, vegetables, fruits, roots, nuts, and wild game. Therefore sugars, salts, oils, and grains and vegetables which came about during the Agricultural Revolution are discouraged.

The claim of the Paleo Diet is that natural selection has not strongly acted on humans since the rise of agriculture, thus humans are maladjusted to the modern diets which they now consume. Hunter-gatherer societies, which still follow the basic ancestral human diets, have overall lower prevalence of disease.

By this reasoning, foods which humans are considered ill-adapted for are partly responsible for the increasing rates of obesity, cardiovascular disease, high blood pressure, Type 2 diabetes, and even cancer. To help avoid the diseases caused by the “modern affluent diet”, humans should follow the Paleo Diet and avoid modern foods.

But, while abstaining from excesses of sugar and oil is beneficial to human health, the actual scientific reasoning behind the Paleo Diet is shaky at best.

1. Lifestyle is a major factor in any diet, not just the Paleo Diet

The lifestyle that the Paleo Diet promotes is itself healthy – growing or hunting one’s own food, and not eating in excess are healthy additions to any diet protocol. The main bulk of the health advantages stemming not from what hunter-gatherer peoples actually eat, but how they live, and their diets are a result of their culture.

Basically, hunter-gatherers are more active and tend to consume fresher foods because they must acquire it for themselves. Any modern American who hunts and gathers their own food will surely already lead a more active lifestyle and is also less likely to consume processed foods and junk food, whether or not they are following the textbook Paleo Diet.

However, the changes that have occurred among urban societies, even in the past century or so, have made following a hunter-gatherer lifestyle next-to-impossible.

The assumption that humans have not changed or adapted to their environment in the past 10,000 years ignores everything we know about evolutionary change. If adaptation comes naturally over time, why should change suddenly stop? While it is true that natural selection may be acting less on populations now with modern medicine and more consistent food sources, but fluctuations in population genetics are always present.

Furthermore, there is evidence that rapid changes have occurred in human populations since the rise of agriculture, and the evolution of lactose tolerance is a good example. A few thousand years ago there was an increased interest in animal husbandry in human populations, which led to more access to dairy products like cheese and milk. Early humans naturally lost lactose tolerance after weaning, but populations with access to dairy have since evolved a genetic ability to continue to digest lactose into adulthood and therfore retain the ability to acquire nourishment from dairy products.

3. Humans are opportunistic omnivores and are designed to eat a variety of diets

The premise of the Paleo Diet is that humans are specifically adapted to a certain diet and are maladjusted to consuming different diets, which has already been proven false by the evidence of change in lactose tolerance. Furthermore, this assumes that all early human groups ate the same diet, which is wildly blind to the fact that human populations arose all over the world and couldn’t possibly have eaten the same foods. And anthropologists can never be sure of the exact diet of any ancient group because it would have been widely variable based on location, season, and food availability.

Furthermore, the fact that humans only had access to certain foods during their evolutionary history doesn’t automatically mean that they aren’t capable of eating other things.

4. Diet alone cannot guarantee health

There is no specific relationship between genotype (one’s genes) and phenotype (one’s physical traits), so even if humans were specifically adapted for a certain diet, genes are not the only factors which influence final health, and environment and early development can have equally strong impacts later in life. Hormones, musculature, and metabolism, among other factors, mean that some people will naturally weigh more or less no matter the diet they follow.

So, while the reasoning and science behind the Paleo Diet seems inaccurate at best, this isn’t to say that it can’t be beneficial to one’s health to follow some of the suggestions it makes. However, strictly following the Paleo Diet based on the belief that you are eating as ancestral humans did won’t be anymore beneficial than any other fad diet out there.

“And of their flesh shall ye not eat, and their carcass shall ye not touch; for they are unclean to you.”-Leviticus 11:8

“Having well considered the origin of flesh-foods, and the cruelty of fettering and slaying corporeal beings, let man entirely abstain from eating flesh.”
-Manusmrti 5.49

“O ye who believe! Fasting is prescribed to you as it was prescribed to those before you, that ye may learn self-restraint … But fear Allah, and know that Allah is with those who restrain themselves”
-Surah 183, 194

Religion can hold a strong sway over culture and it influences how people behave in social situations by placing a strong emphasis on moral behavior and promoting group cooperation. However, the benefits of religion may come at a price and sometimes an individual must forego his or her own personal interests for the good of the religious group, perhaps by becoming a celibate religious leader, payments of tithing, or following dietary restrictions and fasting laws.

Religious taboos that prohibit the consumption of certain foods or food during certain times are particularly interesting because they seem to go against all basic survival instincts that humans have.

Judaism mandates that its followers must keep Kosher, which are foods acceptable to eat under Jewish Law, and there are many restrictions and taboos during the time of Passover, including prohibition of leavened bread.

Followers of Islam should only eat foods that are Halal or “permissible in Islamic Law” and must abstain from consuming any food during the fasting periods in the month of Ramadan.

Catholics may not eat red meat on Friday or during the time of Lent, when it is typical for other forms of luxuries to be given up as well.

Many different explanations for the historical origins of dietary restrictions have been proposed in the past, but research in the fields of anthropology and psychology suggests that the most plausible explanation for these seemingly detrimental rituals is that they signal devotion to a group.

An individual associates with a specific group of like-minded individuals and this membership grants them the benefits of others’ altruistic acts – aid that is given simply because someone is in the “in-group”. Being part of the group therefore provides safety, relationship opportunities, and the possibility of help from a group member. Individuals form a group by entering into a social compact where they all agree to work together and adhere to rules of the group for the greater collective good of all members.

This is known as reciprocal altruism: you help a member of the group because you expect that at some point, they would do the same for you, and everyone wins.

However, this system can only work if everyone follows the rules and if their promises of aid are honest. Otherwise the group breaks down when people invest and are not rewarded. And it is difficult to organize voluntary group cooperation without the risk of some people taking advantage of the system, so-called free riders, that reap the benefits of being in a group without returning the favor.

If a group relies on cooperation and altruism to function, there must be a way to determine who is part of the group, usually through shared behaviors, customs, dress, etc. Common forms of signaling group membership can include clothing style, such as identifying oneself as a Michigan student by donning a blue and maize sweatshirt or identifying oneself as Christian by wearing a rosary or crucifix.

Similar behavior and dress clearly identifies all member of this group as loyal fans to the University of Michigan.

The flaw with these signs of group membership is that anyone who wants to take advantage of the benefits to be reaped from group camaraderie can, and by simply wearing these articles of clothing, they can appear as though they too are part of the group.

A so-called “wolf in sheep’s clothing” can integrate themselves into a group to benefit from it without any intention of returning the favor.

A group’s capacity to find and then punish or oust cheaters increases the overall success of the group, so a more effective and selective form of group identification is often required.

Therefore, a more complex way of signaling group membership may arise in the form of a costly signal. This is a behavior that does not directly benefit the member of the group or the group as a whole, but demonstrates a commitment to the group. If an individual is willing to go out of their way to demonstrate that they want to be part of the group, it is more likely that they have a true vested interest in the group’s outcome.

It can be argued that a dietary restriction or food taboo is an example of this type of costly group signal – health and happiness are not gained by following any such rule (except the happiness one finds in being devout in their religion). Yet, nearly every religion in the history of mankind has requested that its followers obey some sort of dietary law.

An early Judeo-Christian belief held that pork was prohibited because pigs were used by pagans such as the Romans to worship false idols, and therefore the animals were tainted in the eyes of God with a connection to idolatry and were unclean for believers to consume. However, if this were the case, then most domesticated animals should have been considered unclean to eat, because many other animals associated with pagan practices, such as the bull, ox, or sheep were not considered unclean.

This facade from the Ara Pacis in Rome indicates that sheep and cattle were equally important animals in Roman ritual, yet there are few Western taboos regarding the consumption of their meat.

Many different theories and explanations have been proposed for why most major religions demand that their followers obey a variety of dietary restrictions and taboos, and they cite reasons that range from historical symbolism to biological issues. Clearly, traditions in a religious practice have important symbolic meaning for its followers. The practices need not require sacrifice in order to maintain this symbolism, but typically, they do.

But it turns out that where history cannot, evolutionary theory can provide an explanation for the persistence of dietary laws: following dietary restrictions is a way to show one’s commitment to a group and indicate a genuine interest in cooperation and altruism.

Any rule that elicits a food restriction immediately divides people into groups of those who follow it and those who do not. Every culture has special protocols or traditions associated with acquiring or eating certain foods, and food taboos figure prominently into many societies around the world:

A traditional American thanksgiving would not be complete without the male head of household sitting at the head of the table, ready to carve the family’s turkey.

A successful Netsilik Eskimo seal hunt ends when the meat has been meticulously divided among a hunter’s lifelong “seal partners” during a village-wide celebration.

A Catholic communion involves the drinking of wine and eating of bread in a highly symbolic and meaningful way, and only members of the Catholic church may participate in this special event.

These rituals are performed in such a way that anyone who is not a member of that group would not fully understand and would thus be disconnected from the others during celebrations. Consequently, it is easy for others to determine which group an individual associates with through their knowledge of food customs, taboos, and restrictions. Furthermore, anyone willing to follow complicated rules that require a sacrifice of luxury demonstrates they are not simply fair-weather followers but devoted members of the group.

By this obvious outward sign of who is part of the culture, the religion, the “in-group”, dietary laws can function as a way of keeping groups more united because members can be more assured that their fellow group members are equally committed to the group.

Anyone interested in reading more on these ideas should definitely check out my inspiration:

Also, researchers conducted a case study of group membership signaling among religious communes. Their findings indicated that groups which require more commitment, more “inside” knowledge, and more adherence to ritual, were more likely to be successful.

Out of genuine interest rather than any particular career planing, I spent this past summer working an internship at Avian Wildlife Center that rehabilitates and releases injured wild birds, anything from hummingbirds to herons. Most of the birds we dealt with were brought to us after unfortunate interactions with humans in some way – nest disrupted, hit by car, poisoned by pollution, etc. At the center, birds receive care until they can be released back into the wild.

3 little victims of an illegal nest removal, these fledgling American Robins are a few weeks away from release back into the wild

Before release they are also tested for parasites, ability to self-feed, and feather condition. During their time at the center people interact with them as little as possible so they don’t learn to associate humans with food and approach them after being released.

It’s a great and rewarding job, if you aren’t expecting high pay, flexible hours, or a stress-free work environment. It’s also pretty interesting, and I could (and did) leave work every day with multiple bird stories to share.

This baby Lesser Sandhill Crane was everyone’s favorite, and an opportunity to take charge of his bi-hourly hand-feeding routine was a contested role during his visit.

One particularly interesting case we had was a lady who brought in a fallen sparrow nest, with three baby birds. She commented that she was surprised one of the babies was twice the size of the other two. This is because one wasn’t a sparrow at all, but a cowbird. They are incredibly interesting birds, particularly in how they raise their young – they don’t. Instead, they are nest parasites: the mother cowbird flies around laying eggs in other birds nests to be raised by an unsuspecting parent bird, in this case a sparrow.

The lady, who before this information had been impressed by his advanced growth, was suddenly appalled at the poor little cowbird in her sparrow nest. She then asked if we would euthanize the “parasite” since it disrupted the life cycles of the other birds. Of course that is not the case, and we explained that we would take care of it just the same – the center takes any injured wild bird, irregardless of how many individuals of that species they might already have because it makes no attempts to influence natural population ratios.

She wasn’t convinced why it should be saved, which was a common sentiment among several of the rescuers of cowbirds we spoke to over the summer.

Perhaps the term “parasite” gives them a bad reputation, but cowbirds are truly fascinating. Where most other species would imprint on whatever they first see – imagine the classic example of a baby duckling who imprints on a human when it hatches and spends its day following people instead of fellow ducks. Cowbirds, however, are smart enough to know what they are without having to see another cowbird during their whole infancy. This is because they recognize their own coloration and use that information to find mates in the future.

Though barely related, I had to include this image of 2 ducklings imprinted on a Corgi

Generally, to the public we simply try to explain that it is the bird’s natural behavior which should not be tampered with. Cowbirds are not an invasive species and are completely meant to coexist with other birds in their natural habitat, which ranges all across North America from southern Canada to southern Mexico.

They can’t thrive without this method of reproduction, which arose naturally through co-evolution with competing bird species. It is simply how they live and reproduce, and the individual should not be blamed for its innate biological behavior, any more than a hawk should be blamed when it kills a dove for its dinner.

This isn’t to say that cowbirds don’t harm other birds – I am sure that unknowingly raising a baby cowbird takes its toll on a sparrow mother, who will be half the size of her baby before it leaves the nest. But they don’t outright kill their hosts (a good parasite doesn’t kill its host, or it loses its livelihood), and the parents with whom the cowbird tries to leave her eggs are not completely defenseless in the matter, as they sometimes detect and eject foreign eggs.

Cowbirds are known to parasitize over 100 different species, so their eggs seldom match those they are laid with. Here, a large speckled cowbird egg is alongside 3 smaller blue Chipping Sparrow eggs.

Still, there is so much love (and funding to care for) birds of prey, who must kill to consume at least 20% of their body weight a day to sustain themselves. People marvel over the beauty of an eagle soaring in the sky while nest parasites, such as cowbirds, cuckoos and several other species, are met with animosity – even though they are usually not responsible for the deaths of any other birds and are equally fascinating creatures.

(An exception is if a cowbird egg/baby is discovered and tossed from the nest by the duped parent. A response, nicknamed the “Mafia Behavior”, occurs where the mother cowbird will return to the nest and destroy the other eggs, in hopes of forcing the victim to create a new nest and lay a new brood, also giving her another chance to lay new eggs).

Cowbirds are somewhat infamous for contributing to the near extinction of the Kirtland’s warbler and there were even several mass attempts to remove cowbird eggs from warbler nests, although later it was found there were several other factors leading to their decline besides cowbirds, mostly from human damages to the ecosystem. And studies have even shown that when humans try to remove cowbirds, we end up helping them – removing birds from an area signals less competition, so they are able to reproduce more in that area and end up parasitizing even more nests than they would normally would have.

As with any animal that makes its way through life by competing with others, there are winners and losers. As a rehabilitator, helping one means eventually harming another, as the circle of life continues in the wild and someone must be preyed or parasitized upon. That doesn’t mean efforts to protect the environment are any less meaningful and perhaps the best thing we can do is try to fix the damages done by humans and restore the balance that existed before human activity began to cause serious disruptions.

After all, these species got along just fine before humans showed up to observe, monitor, and “fix” nature.

I am currently in an anthropology class that focuses on how food perspectives, nutrition, and diets have shaped human evolution. It focuses on what we eat and why, and the cultural impacts of these beliefs. Naturally, the phrase “tastes like chicken” came into the discussion on day #1 and it piqued my curiosity about the origins of the phrase and whether it was actually true.

First off, the origins of the phrase seem to come from the late 19th century, when a European writer described eating a rat in China as having the consistency, texture, and taste of chicken. Since then, it has become a common, often comedic phrase, used to describe a variety of foods – sometimes describing things that actually taste like chicken, or something that is bland, or something that is exotic or strange.

My first instinct on the possible accuracy of this phrase, being an evolutionary anthropologist, was that perhaps all of the animals that supposedly taste like chicken originated from one common ancestor that tasted like chicken, or more accurately all things that taste like chicken actually taste like this common ancestor.

The flavor of meat can be based on the evolutionary origin of the animal, due to chemical make-up of the animal’s muscle tissues and other factors that influence taste. As it turns out, species descended from tetrapods tend to taste like chicken – i.e. birds and reptiles. Hoofed animals diverged from the tetrapod lineage, explaining why they have a different flavor than the rest of the animals we eat.

This is a phylogenetic tree, or visual representation of evolutionary history, of the species of animals that reportedly taste like chicken. Note the divergence of the hoofed animals and the differing flavors of their descendants.

This brings up the fun theory that because dinosaurs were the evolutionary predecessors of birds, they probably tasted like chicken too.

Of course, my explanation of the evolutionary theory of chicken flavor was promptly shot down by a friend majoring in biochemistry (you know who you are, buzzkill). He declared that the real reason that some things taste like other things is their glutamate content.

Flavors in meat are partially due to glutamate, an amino acid derivative that seems to contribute to the “savory” flavor of meats. Research shows that chicken has a lower glutamate content than many other meats, which results in the bland flavor that chicken can have, making it a more universally-comparable flavor.

While I agree with his explanation, I disagree with his disagreement of my theory. If studying anthropology has taught me anything, its that there is never just one simple answer to anything. So often, especially in the field of evolutionary biology or evolutionary anthropology, people are quick to judge one theory as being wrong or against their beliefs. But the important thing to remember about evolution is that it is not mutually exclusive of any other fact – instead it works with these facts to help explain how and why they came about.

Which leads me to the last point about this whole article – anything I have said here does not actually make much sense because different subspecies of chicken, age of chicken, cut of chicken, flavoring, cooking method, etc. can all have huge influences on flavor so there is really no way to say that something tastes like chicken when there is really no definitive “chicken flavor”. It’s all really just fun food for thought.

Even foods that say they taste like chicken don’t really taste like I imagine chicken to be.